Tests

Monday

Carl Heneghan

How many Covid diagnoses are false positives?

Test, test, test said the WHO. And globally, that’s what everyone did: tests have detected more than 14 million cases of Sars-CoV-2 so far. The thinking goes: turn up, have your test, and if positive, you must have the disease. But that’s far from the truth. When virus levels in the population are very low, the chances of a test accurately detecting Covid-19 could be even less than 50 per cent – for reasons that are not widely understood. There are two issues about tests to get your head around. The first is the sensitivity of the test: the proportion of people who test positive, out of the population who

Friday

Steerpike

How did Matt Hancock hit his 100,000 test target?

Matt Hancock has announced that the government has managed to meet its 100,000 coronavirus tests a day target. The Health Secretary confirmed at a Downing Street press conference that on 30 April, Public Health England carried out 122,347 tests – suggesting the government not only reached its target in time, but also over-delivered. But look at the small print and there were barely 73,191 people tested yesterday. There is another mysterious second category, now introduced, that takes the figure over 100,000. Here’s the graph: So what’s the trick? The Health Service Journal reports that to reach the testing target, the government has begun to count home-testing kits which have been posted